An overpressure wave is a transient air pressure, such as the blast wave from an explosion, which is greater than the surrounding atmospheric pressure. Such overpressure waves originate at the point of detonation of the explosion and typically propagate outward from the point of detonation in all directions. Such explosions may also involve the release of intense heat.
Various methods are often employed to cause an overpressure wave to be directed in a desired direction. For example, directed charge methods might involve placement of an explosive against an object capable of sustaining the blast (e.g., a thick concrete structure) so that the energy of the explosion will be directed outward from the object. Similarly, various methods of ‘shaped charges’ are used to cause the majority of the energy of an explosion to be directed in a desired direction. Similarly, blast barriers such as concrete walls or earthen berms are often used to redirect the energy of potential explosions away from valuable assets such as buildings. Great Britain patent GB 1,269,123 describes detonation of ethylene and oxygen in combustion tubes and use of the detonation wave for coating, to drive a turbine engine, and for rocket propulsion. U.S. Pat. Nos. 4,662,844 and 4,664,631 describe igniting fuel and oxidizer mixtures within combustion chambers to produce a detonative combustion wave to simulate weapons effects. U.S. Pat. No. 5,864,517 describes a pulsed combustion acoustic wave generator to produce acoustic waves that can be used for non-lethal incapacitation, impairment, or immobilization for crowd control or self defense; mine detonation; wildlife control; acoustic cleaning; and triggering avalanches. These methods are similar in that they cause an overpressure wave to be directed out of the open end of a detonation tube. As such, various methods exist for directing overpressure waves.
It is desirable, however, to have an improved system and method for generating and controlling overpressure waves for useful purposes.
Seismic shock waves introduced into the ground are often used in geophysical exploration systems. Such seismic shock waves are typically introduced, or conducted, into the ground using either explosives or a vibration coupler. The use of explosives for such purposes is dangerous, expensive, and the resulting blast is difficult to control precisely. The transportion of a vibration coupler typically requires a 5- or 10-ton truck and it is time-consuming to set up.
Great Britain Patent 934,749 discloses an acoustical generator and seismic exploring system where an open ended combustion chamber is used to generate acoustic energy pulses that are directed downward into water or at the ground and a seismic detector is used to detect reflections of the pulses for seismic surveying.
U.S. Pat. Nos. 3,235,026 and 4,043,420 describe closed detonation chambers attached to the ground via bottom plates where a detonation of a oxygen-fuel-oxidant mixture produces a shock wave that applies a compressive inpulse against each bottom plate and the surface of the earth on which it rests thus initiating a seismic wave into the subsurface. The patents disclose alternative forms of shock absorbers that cause an opening in the detonation chambers to vent exhaust fumes.
U.S. Pat. No. 5,864,517 states “by introducing sound waves into the ground and recording their reflections, scientists can determine the composition of the earth's sublayers” and that a pulsed combustion acoustic wave generator “could generate precise sound waves at exact intervals to increase the amount of information that could be gained” from geophysical exploration studies. This prior art however does not teach how such precise sound waves at exact intervals can be generated.
An alternative geophysical exploration approach invented by the present inventor and described in U.S. Pat. No. 6,360,173 uses a detonation tube as an impulsive seismic source to generate a sequence of time-coded monocycle waveforms that propagate to geophysical structures and/or properties causing the geophysical structures and/or properties to return echoes, and a sensing means for sensing data that are representative of the echoes.
It is desirable to have an improved system and method for introducing energy into the ground or another media for exploration purposes.